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UNIVERSITY OF LONDON

 

POSTGRADUATE MEDICAL SCHOOL
OF LONDON

Telegrams

POSGRADMED CHISK LONDON DUCANE ROAD
Telephone LONDON, W.12
SHEpherds Bush 1260 (4 lines)
Department of
Bacteriolopy.

3th April, 1952.

Dear Dr, Lederberg,

I had intended to write you a detailed letter when [ hud
some leisure aftcr the Soc. Gen. Microbiol. meeting next week
but have been prompted to do so now by a letter from Gavalli
this morning saying thet you and he would like to publish your
paper on F+ trensduction in the J. Gen. Nicrobiol., preferably
in the same issue as mine would annpear, and that your joint
paper should be resedy by the end of the month. Let me say at
once that I think this is very nice of you both and that I will
be only too pleased to co-operate. However, I don't went to
appear in any way Machiavellian (which I am not!) and thoasit I
should let you know at once of snme recent wor: which I have
done which I think seriously undermines sny orthodox internret-
ation of recombination in K-12 as a more or less classical sex~
ual process. Iam afraid I cannot go into exnerimental eetsil
now but can only give you a resume of my resilts. Hovever T
feel that my technique and method are sound end thot you can
accept the results as valid. Incidentally, let “s say in ud-
vance that my "unorthodoxy" is largely due t> a poor knowledre
of classical genetics so that I do not instinctively internret
findings in renetic terms. I do not hold stronely to my theory
and am quite ready to abandon it if need be, and I cannot atterpt

to fit my findings into a detailed fenetic picture witnont expert
advice.

/iccording to you
1. According to you, F+ is separate from the "gamete" and
determines self-compatibility; -1.e. determines the ability of
the two mutants to mate by means of a more or less orthodox
sexual mechanism in which both partners participate more or
less equally, If this is so, then F+ x F+ matings should be
more efficient that F+ x Fe matings since, in the former, all
the cells are compatible ab initio, while in the latter, mating
mist occur in two stages - first the transduction of F+ to the
Fe cells and then the actual mating between the now compatible
F+ cells. On putting this to the test, I found that 53-161/i+
x W677/i+ is approximately twenty times less efficient in
prototroph formation than either 58-161/F+ x 677/F= or A677 /B+
x 58-161/F-. I have repeated this twice und am confident thet
it is so.

26 As I see it, if recombination is achieved by tie union of
two complete haploid chromosomes, with crossing over und meiosis,
then the patterns of unselected markers should be the same ire
respeotive of which partner of the mating mixture initially
carries F+ or F-. I have in the past tested severs! niundred
prototroph colonies from the usual 53-161/F+ x ‘677¥F- iete and
have been struck by the fact that 25 - 30 per cent huve the

W677 ("gene acceptor") phenotype. The marers I have used ave
been Lac, Man, 91 and 9T3. I have now tested 20 prototroph

/Colonies from each
UNIVERSITY OF LONDON

 

POSTGRADUATE MEDICAL SCHOOL
OF LONDON

Telegrams

POSGRADMED CHISK LONDON DUCANE ROAD
tesphene LONDON, W.12

SHEpherds Bush 1260 (4 lines) )
ft a epee

colonies from each of the F+ x F+ and F+ x Fe motings specified
above. I find that, using these markers, the majority of

prototrophs carry the phenotype of the F- ("gene acceptor")
strain und none that of the F+ strein when one of the strains

is frankly F- while in the F+ x F+ cross the phenotype of the
prototrophs is (apart from "new" strains) either thot of 53-161
or of ‘677 in about equal proportions. These results sre quite
clearcut and, although I heave only done this exveriment onee, I
am sure thit they will prove repeatabie,

  
   
    
  
 

I shall be most interested to lesern your views, St the
moment I am trying to formulate my own for my forthcoming_»:
I still hold that an F+ strain is one which hertours a C;
and, like lysogenic cells in relation to phage, cannot rc-cetv
one until it has got rid of its own; while F-{ cells are “gam te'~
free. I think it possible that some of the "blocks" of TONES
which the "gumete" carries can perhaps show genuine reeombination
with parts of the F- chromosome but thet the busie renctie struc
ture of the prototroph remains that of’ the “accentor" strain.
Perhaps the number of "" are an index of the Vamlences of vy views
but I feel that the detoils ere really a matter for the venetizict.
It may be that the K-12 type o> recombination is the siissing Lin’c
in the evolution of sexusl mechenisms from simple traastor~stions
and all the more intcresting on thut account.

Spicer tells me that he is going t>) work in your lah. in the
near future, T would very much like to have the opportunity to
discuss things with you personally but cen't see a hone of retting
to America in the forseeable future, But perhans you will be

coming to “urope! I thought your "Selected Papers” excellent and
a most valuable book to possess.

Yours sincerely,